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Harold McGee on Coffee and Tea

What do you think of the new Starbucks powdered coffee? (Dare I ask?) Could this type of powder be replicated by consumers at home with a powerful blender and some good coffee? Or tea?

A.

Instant coffee powders are made by brewing coffee, evaporating all the water from the brew under a vacuum, and then adding back aromatics that are lost during the evaporation. Not something you can approximate in the home kitchen.

Q.

What is the best way to make a cafe Americano?

A.

An Americano is a small, concentrated cup of espresso diluted to standard brewed-coffee strength with hot water. So the key to a good Americano is starting with a good espresso. And making good espresso is a long story.

Q.

Are the more reputable nonorganic tea gardens known for excessive pesticide use? What types/quantities of pesticides are needed in the typical tea garden? The reason I ask is that I can’t seem to locate a reliable source for whole-leaf organic green or white tea in sachets, so I usually end up buying conventional (e.g., nonorganic) whole-leaf green tea sachets from a top-shelf vendor.

A.

Common teas are blends of leaves from many growers, so I don’t think it’s possible to generalize about their probable pesticide exposure. There are purveyors of unusual and high-quality teas that also offer tea in sachets — Harney is one example — and I would trust them to have high standards for everything they sell.

Q.

What is the best method for making iced tea? Is it best to brew a very concentrated hot tea, then add water and ice? Or is it preferable to brew the tea at ordinary strength and cool it down later, adding ice just before serving?

A.

The “best” way to make iced tea depends on your personal preference and how quickly you want it. Hot-brewing a concentrated tea and adding ice will give you a flavor closest to fresh-brewed hot tea, and it will get cloudy with substances that are soluble in hot water but not in cold. Hot-brewed tea that cools for hours won’t taste as fresh, and will also get cloudy. Cold-brewed tea will have a simpler aroma, and will stay clear. Give each a try and pick the one you like best.

Q.

Cold-brewed hibiscus flowers I know as sorrel, usually with some slices of ginger added to the mix as it sits for a day.

A.

Hibiscus sabdariffa came originally from Asia and east Africa and has a number of different names across the swath of the planet from here to there, including Florida cranberry, sorrel in the Caribbean, jamaica in Latin America, and karkadé in north Africa and the Middle East. Try this recipe.

Q.

In your column, you write that simply chilled coffee makes “a cloudy, less flavorful drink on its own, one that benefits from mixing with milk or cream and sugar.” Why is this? What’s the chemical reason that hot coffee that has simply been chilled is inferior to double strength hot brewed coffee that has been diluted with ice?

A.

The main difference between chilled regular coffee and ice-diluted double-strength coffee is time. Hot coffee contains hundreds of different chemical substances that immediately start reacting with one another and with oxygen from the air. And these reactions go much faster at high temperatures. The more time the coffee substances have to react, the more the flavor changes. So coffee that is chilled and consumed immediately will taste fresher than coffee that has cooled slowly over the course of several hours. You’re less likely to notice the difference if you mix the coffee with milk and sugar.

Q.

Would different sources of water change the infusion? If so, which properties would be ideal?

A.

Coffees and teas are about 98 percent water, so water quality is important, especially if you’re making a cold brew. Bringing water to the boil can drive off chlorine and other unpleasant aromas, so if your tap water has some of these, you might want to boil and then cool it before brewing. Hard water, high in calcium and magnesium minerals, will significantly slow the extraction, so if your brews seem consistently too weak, try using bottled spring water.

Q.

I found a real tasty iced coffee concentrate at the Brooklyn Kitchen called Grady’s Cold Brew. It advertises itself as “New Orleans Style.” What on earth does that mean?

A.

New Orleans coffee often includes chicory, but cold-brewing also goes way back down there, so the term may just refer to that tradition.

Q.

Is it safe to let steeping tea sit for 6 – 8 hours at room temperature? That’s what I’ve always done, but have recently heard it’s best to do it in the refrigerator to avoid culturing bacteria in the tea at room temp. Is this so?

A.

Steeping tea in the refrigerator will certainly slow any growth of disease-causing bacteria that might otherwise occur. It will also slow the extraction. I haven’t found any evidence in the medical literature that brewing tea at room temperature poses a significant health risk.

Q.

Is there any real scientific basis to the AeroPress Coffee Making System. The company says less contact between the ground coffee & the hot water reduces acidity. It’s an awkward system to employ.

A.

15. The AeroPress device has plenty of fans and does make a good cup of coffee, though it’s true that it’s not the simplest system for doing so. The low acidity comes mainly from brewing with water well below the boil — as I recall, somewhere around 170 degrees.

Q.

I drink iced coffee in summer, and hot coffee in winter, brewing both hot with freshly ground beans, and a drip coffee maker. My cold coffee is cloudy after being in the refrigerator. What can I do to avoid this?

A.

Hot-brewed coffees and teas eventually cloud when chilled because the temperature change causes some of the dissolved materials in the brew to precipitate, or form fine solid particles. Most of the soluble materials — caffeine, acids, phenolic substances — are much more soluble in hot water than cold water. The hot brewing dissolves lots of solubles, and when the temperature falls and the cold water can’t keep them dissolved anymore, they form solid particles. Cold brewing never dissolves more solubles than cold water can hold, so it doesn’t cloud.

Q.

Most of us grew up on “sun” tea — tea bags in a clear jar filled with water and left in the sun to “brew.” Is this method still a good choice for those of us with less refined palates? Is there a simple way to make good iced tea at home without buying special equipment?

A.

Cold-brewing tea doesn’t require any special equipment. A pitcher and strainer work fine.

Q.

Much has been made of brewing coffee at the proper temperature, but what about the proper grind? Those of us with burr grinders at home have a wide range of grind settings, and numbers marking them that are only relevant to that particular grinder. Within a broad category of grind, say for filter drip, is a grind on the finer end of the spectrum better or worse than a coarser grind?

A.

The grind — the size of the coffee particles — is indeed an important variable in brewing, both because it affects how quickly the particles are extracted, and how quickly water flows through the grounds and filter and thus how long it stays in contact with the grounds. For filter drip you want a medium-fine grind that will take three or four minutes to brew.

Q.

If making high-quality coffee concentrate is so easy, why aren’t such high-quality concentrates commercially available? Sure, low-quality ones exist for the food-service industry, but they’re nothing close to good-quality coffee.
Also, is oxidation a problem when making homemade concentrate?

A.

Stumptown is now selling bottled coffee prepared from cold-brew concentrate, but not the concentrate itself. I wouldn’t be surprised if concentrates comes to market soon. Some coffee pros claim that prolonged brewing and storage cause oxidation, but I don’t notice any staleness in cold brews over the course of a few days.

Q.

Several of my colleagues swear by the AeroPress plunger system, and it does seem to make an awfully good cup of coffee. But I’ve seen differences of opinion online about whether what it produces is actually espresso. Would you please weigh in on that?

A.

I would agree that AeroPress makes a good concentrated cup, but it’s not an espresso for many reasons, among them that it filters out oils and other materials that produce the unique espresso flavor and body.

Q.

Why do so many of these coffee preparations call for making double-strength (or more) coffee, which then must be diluted? Why not make regular strength and, for instance, use coffee ice cubes instead of water ice cubes?

A.

There are lots of ways to make cold coffee, and brewing regular-strength coffee and cooling with coffee ice cubes is yet another with its own pros and cons.

Q.

In the summer I drink iced coffee daily, so I bought the Bodum French press specifically for cold brew. Tried it once (steeped overnight in the fridge) and the result was extremely weak — not even drinkable. I did use quite a bit of coffee (followed Bodum instructions), but your article indicated 1/2 pound to just 5 cups of water … yikes, that could get pricey. Or is this supposed to make a concentrate? Can you give specifics on making (strong) cold brew coffee? Thanks!

A.

Yes, the half-pound coffee to five cups water gives you a concentrate that you dilute about 3 to 1. Not that expensive in the end, and you can adjust the dilution to your own taste.

Q.

Are there health risks involved with preparing coffee and especially tea when the dried ingredients aren’t subjected to hot water (which could presumably kill or neutralize harmful substances)? I have read in the past that tea makers do not recommend preparing their product without very hot water for precisely this purpose.
I’ve been told that sun tea, which seems to be another name for cold-brewed tea, is unsafe because it can contain bacteria that were on the tea leaves. What is your opinion ?

A.

It’s true that there can be bacteria on tea leaves, that cold brewing won’t kill them, and that there is therefore some risk of food poisoning from cold-brewed tea. I haven’t found any evidence in the medical literature that it’s significant.

Q.

I was wondering why restaurants seem to think it is a good idea to leave tea leaves/bags in their tea for long periods of time after brewing is finished. I was taught that the tea should be removed from the water after its optimal brewing time (four to five minutes usually) so that the tea doesn’t get overly strong and bitter. This preserves the taste of tea, and doesn’t ruin what’s left in the pot for the second cup. However, almost every time I go to a restaurant and order a pot, the leaves are dumped in there, or the bag is solidly wound around the lid so I can’t get it out, which means I get one really good cup, and the rest I can’t even drink. Why is this the norm? Am I just in the wrong?

A.

You’re right, the longer you leave tea leaves in the tea after optimal brewing, the more bitter and tannic it gets. What you describe is unfortunately common brewing malpractice.

Q.

In Asia we drink Chinese tea by infusing the tea leaves several times, making more than one brew. Sometimes the tea leaves are held over from the night before, especially if the tea is a very expensive variety, e.g. Long Qin (Dragon’s Well). Do you think this is a food-safe practice?

A.

Chinese green tea is usually brewed with water near the boil, and repeated brewing extracts doesn’t leave much for bacteria to grow quickly on, so I wouldn’t be too worried about the safety of reusing leaves the next day.

Q.

I’m thrilled to have the opportunity to ask this question of you, Mr. McGee, as I’ve literally said to friends, “I need someone with a science background to explain to me why coffee (beans and grounds) smells so good before I make it, but if used grounds sit around (e.g., in the garbage), they smell like garbage — and pretty quickly.” Is there a scientific change that occurs once the water and heat hits the grounds that affects the smell?

A.

When you brew coffee, you extract much of the desirable aromas of the roasted beans from the grounds. The aromas left in the grounds react with the water and oxygen in the air and become less and less like the pleasing original.

Q.

I have a question about cold-brewed coffee. You say that this contains less caffeine than hot-brewed, but the cold-brewed that I’ve had recently (Infinite Black from Dunn Brothers) feels like it has much more caffeine than hot. Your thoughts? My question about iced tea is that if I make a large quantity of black or green tea and then refrigerate it for later use, it gets cloudy and bitter. (This is also a problem in restaurants, which makes me reluctant to order iced tea out.) Any tips on this? Right now I just brew extra-strong hot tea (of all sorts) and pour it over ice.

A.

It’s hard to generalize about caffeine levels in coffee and tea, because they depend on the original coffee or tea and many details of the brewing process, including how strong the final cup is. Because cold-brewed coffee is much less bitter and astringent than hot-brewed, it might be served stronger and so deliver more caffeine despite containing less caffeine at standard strength.

Q.

My question is about jamaica (hibiscus). I had it once and had violent stomach cramps afterward. I read it causes gastrointestinal symptoms in animals who accidentally ingest it. It’s quite popular in cocktails and iced drinks. Any truth to the GI connection?

A.

I haven’t found any evidence that adverse reactions to hibiscus are common. Unlike coffee beans and tea leaves, hibiscus calyxes aren’t treated with high heat, so it’s possible that a poorly handled batch could have been contaminated with undesirable microbes.

Q.

I am curious about the acidity of coffee that has been steeped for a long time, even in cold water, compared with the acidity of coffee that has been brewed quickly and chilled. I have recently switched to an AeroPress and like the results for hot coffee; the acids don’t have a chance to develop and take over my cup as they did when brewing automatic drip coffee. I am convinced that a short duration of time in contact with hot water is the ticket for the tastiest coffee with the least acrid dimension; it works for my traditional espresso maker, too, in which a perfect cup takes about 30 to 35 seconds to pass through the coffee. But how does steeping time affect coffee’s acidity in the cold-brewing method?

A.

Brewing temperature also has a strong effect on acidity. In my kitchen, cold-brewed coffees are consistently higher in pH, lower in acidity, than hot brews.

Q.

Can you use a French press to make coffee concentrate? If so, would you please provide me with the directions for doing so?

A.

A French press is less than ideal for cold brewing because it doesn’t do a very good job of filtering the brew from the grounds. The residue of fine particles clouds the brew and roughens the body.